In the pharmaceutical, building materials and food industries, on vessels and silos, on platforms and dosing systems, right around kitchen and bathroom scales ? weight is measured everywhere. In industry, it becomes particularly interesting with regards to the level in vessels. There are numerous possibilities for weight measurement or weighing. The filling level could be determined optically, hydrostatically, by ultrasound, microwaves and radar, mechanically, capacitively, by heat dissipation, by displacement and resistance or, what this article is about, gravimetrically.
Trapped comprises the Latin ?gravitas? for ?gravity? and the Greek ??? ??????? for ?measure?. In gravimetric measurement, therefore, the heaviness of the mass is combined with the weight force to create a meaningful value and therefore the level depends upon weighing vessels (the filling level results from the density of the medium and the geometry of the vessel). This makes gravimetric level measurement a part of weighing technology.
Gravimetric level measurement is particularly suitable when uneven distribution can occur within the vessels.
Gravimetric level measurement: Advantages
This sort of weighing has several advantages. Possibly the greatest advantage is that the force transducers useful for gravimetric level measurement are located outside the vessel. Thus, they don’t come into contact with the product. Neither is it necessary to open or modify the vessels. Contamination can thus be eliminated. Cleaning can be easier. Furthermore, very precise measurement can be done ? 0.02 % of the rated load is not uncommon when it comes to relative linearity error. This makes dosing possible when, for example, food is filled into bags ? not to mention the packaging must contain the amount specified.
Another advantage is that the merchandise will not influence the measurement. The level could be determined gravimetrically for all contents ? solids, liquids, viscous substances, foaming substances ? even toxic or aggressive contents can be considered. Furthermore, the measurement is not falsified even though voids or uneven contents distribution occur inside the silo or tank, because the entire contents are weighed.
Suitable mounting modules not merely ensure that the weight force is properly led into the force transducers, they also make installation super easy. The module and force transducer have a low height and a little installation volume. However, it might be problematic if the vessels are already permanently installed and can only be placed on modules with significant amounts of effort. Then it really is probably advisable to bolt strain transducers to the supports. Any risk of strain transducers determine the compression of the supports due to the weight of the contents. They thus make it possible to weigh immovable vessels gravimetrically.
Gravimetric level measurement: Disadvantages
The disadvantages of gravimetric level measurement vary in significance according to the application. Email address details are mainly distorted when force shunts can’t be prevented. Ideally, the vessel should be mechanically decoupled. Used, however, it can always happen that, for example, struts are absolutely necessary. Then it depends on how great their supporting effect is. Similar problems can occur if the measurement is influenced by way of a high bearing weight. Volatile of the vessel compared to the product, the more accurate the gravimetric measurement. Finally, free-standing outdoor vessels can be suffering from natural factors. For example, if wind pushes or snow results in a significant increase in weight.
Typical force transducers for the weighing of vessels
Single point load cells are classically useful for scales. These not merely have a minimal price and high accuracy, but the weight can be determined reliably, regardless of where it is placed on the platform. For optimal force introduction, bending or shear beams with the corresponding weighing modules are often installed under tanks, silos or vessels that stand on supports. To look for the rated load of these force transducers, divide the total weight of the vessel by the amount of supports. If the rated load exceeds 10 t, you’ll be able to switch to compression force transducers, the maximum capacity which reaches around 300 t. With four supports, vessels of up to 1,200 t can be weighed with the best accuracy. Alternatively, vessels can be suspended from S-type force transducers or fitted with strain transducers.
Note
Level could be measured in many different ways. Whether gravimetric as described, or with a submersible pressure sensor, float switch or pressure sensor ? WIKA gets the right sensor for every application. Do you want to buy the products? Inside our WIKA online-shop you will discover some of our standard designs. If you have any questions, your contact will gladly help you.
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